Tab element

ABSTRACT

Apparatus for fabricating a tab element having an opening for joinder to a container wall including a female die having an elongated recess and an outwardly disposed annular tab engaging surface. A male die having an upwardly directed boss and a surrounding annular tab supporting surface. The male die having a concave transverse wall connecting the die boss with the annular tab supporting surface. Aligning the tab opening with the die elements and establishing relative closing movement between the dies produces compressive reforming of the opening defining portion of the tab element to provide a convexly curved portion corresponding in curvature to the male die concave transverse wall. A method of reforming an opening defining wall in a tab element to provide a continuous wall which diverges from the upper tab surface to the lower tab surface by compressively reforming the continuous wall. A container wall having a removable sector with a tab element secured thereto by means of an integral rivet including a wall panel having a hollow integral rivet provided with a transverse end wall and a peripheral wall. A tab element having an attachment opening defined by a continuous wall and the rivet extending through the tab element with the continuous opening defining wall in contact with the peripheral rivet wall. The opening defining wall having a lower inwardly convexly curved portion in surface to surface contact with a portion of the peripheral rivet wall having an outwardly concave configuration.

ilnited States Patent [191 Diekhoff et a1.

[ TAB ELEMENT [75] Inventors: Hans H. Diekhoff, Greensburg;

Howard D. Schrecker, Hyde Park, both of Pa.

[73] Assignee: Aluminum Company of America, Pittsburgh, Pa.

[22] Filed: Sept. 20, 1971 [2]] Appl. No.: 181,807

Related US. Application Data [62] Division of Ser. No. 20,705, March 18, 1970, Pat. No.

[52] US. Cl. 113/1 F, 113/l16 CC, 113/121 C, 72/335 [51] Int. Cl B2111 51/26 [58] Field of Search 72/379, 335, 336; 113/15 A, 15 R, 116 CC, 121 C, 121 R, 1 F; 220/54; 29/522 [56] References Cited UNITED STATES PATENTS 3,366,086 l/1968 Fraze 113/121 C 3,447,357 6/1969 l-lo Chow 72/377 3,659,740 5/1972 Diekhoff et a1.... 220/54 2,341,462 2/1944 Matson 72/336 Primary Examiner-Charles W. Lanham Assistant ExaminerM. J. Keenan Att0rneyArnold B. Silverman [57] ABSTRACT Apparatus for fabricating a tab element having an June 26, 1973 opening for joinder to a container wall including a female die having an elongated recess and an outwardly disposed annular tab engaging surface. A male die having an upwardly directed boss and a surrounding annular tab supporting surface. The male die having a concave transverse wall connecting the die boss with the annular tab supporting surface..Aligning the tab opening with the die elements and establishing relative closing movement between the dies produces compressive reforming of the opening defining portion of the tab element to provide a convexly curved portion corresponding in curvature to the male die concave transverse wall.

A method of reforming an opening defining wall in a tab element to provide a continuous wall which diverges from the upper tab surface to the lower tab surface by compressively reforming the continuous wall.

A container wall having a removable sector with a tab element secured thereto by means of an integral rivet including a wall panel having a hollow integral rivet provided with a transverse end wall and a peripheral wall. A tab element having an attachment opening defined by a continuous wall and the rivet extending through the tab element with the continuous opening defining wall in contact with the peripheral rivet wall. The opening defining wall having a lower inwardly convexly curved portion in surface to surface contact with a portion of the peripheral rivet wall having an outwardly concave configuration.

5 Claims, 8 Drawing Figures TAB ELEMENT This application is a division of parent application Ser. No. 20,705, filed Mar. 18, 1970, now U.S. Pat. No. 3,659,740.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for producing a tab element adapted to be secured to a removable sector of a container wall by means of an integrally formed fastener. More specifically, this invention relates to such a tab having a uniquely configurated fastener receiving opening adapted to provide intimate engagement between the tab element opening and the fastener.

2. Description of the Prior Art In recent years containers having wall portions provided with a removable sector and anoperating element such as a lever pull tab secured thereto in order to facilitate severance of the removable sector have become increasingly popular. Particularly advantageous use of such devices has been found in container walls made of metal, such as aluminum, which are employed as can ends, jar and bottle closures and the like. In forming such structures, the removable sector is generally defined by providing a weakened line as by scoring.

The tab element has been frequently secured within the removable sector by means of a hollow integral rivet formed from the material of the container wall. One known method of forming such a rivet is to draw an enlarged hollow boss or bubble in the wall panel and subsequently reform the same into a hollow rivet having a transverse end wall and a peripheral wall. A pull tab provided with a fastener receiving opening and a gripping portion is placed on the wall in such fashion that the hollow rivet extends through the fastener receiving opening of the tab. The hollow rivet is then headed in order to complete the joint and secure the tab in place. In gaining access to the contents of the container, the user lifts one end of the tab which is generally so designed as to provide a lever advantage and moves the same in SI-C'I fashion as to create stresses which initiate score line fracture and permit ultimate separation of the removable sector.

One of the problems frequently encountered with such opening devices is undesired fracture of the rivet during tab element operation. This results in removal of the rivet or a portion thereof from the remainder of the wall and failure to separate the removable sector from the remainder of the container wall. As a result, the user is required to seek alternate means of gaining access to the container interior. One of the common sources of rivet fracture has been undue thinning of the metal about the base of the peripheral rivet wall in the region of the transition between the rivet wall and the remainder of the wall panel. This problem is particularly acute with respect to thinner gauge materials such as aluminum sheet having a thickness of about 0.008 to 0.009 inch. In an effort to reduce the amount of thinning occurring in this region efforts have been made to increase the wall thickness of this portion of the rivet. Such efforts have resulted in the base of the rivet wall having an outwardly concave curved configuration.

In forming the rivet receiving opening in tab elements, it has been customary to punch an opening in the tab corresponding in size to the exterior of the rivet peripheral wall. This has resulted in a generally cylindrical tab opening of uniform diameter throughout its height. This combination of a concavely curved rivet outer peripheral wall and a cylindrical tab opening tends to contribute to imperfect mating between the connecting tab and rivet surfaces. When the rivet is headed or staked, the enlarged rivet head diameter does prevent separation of the tab and container wall, but optimum seating and complementary surface to surface contact between the tab element opening and the rivet peripheral wall are not obtained. This imperfect mating of surfaces reduces the effectiveness of operation of the opening device.

SUMMARY OF THE INVENTION The above discussed problem has been effectively solved by the method and apparatus of this invention which produces complementary curved surfaces on the tab opening and rivet peripheral wall in order to provide effective tab seating and rivet engagement.

The apparatus and method of this invention provides for the use of a female die having an elongated recess and an outwardly disposed tab engaging surface and a male die having an upwardly directed boss and surrounding annular tab supporting surface. A concave transition wall connects the male die boss with the annular tab supporting surface. A tab having a generally cylindrical rivet receiving opening is interposed between the dies and aligned therewith. Relative closing movement between the dies produces compressive reforming of the lower portion of the tab element opening defining wall to reform the same into a convexly curved configuration which corresponds in curvature to the peripheral wall of the integral rivet. This carefully controlled compressively established curved portion of the opening defining wall has a radius of curvature which corresponds to that of the curved peripheral wall of the integral rivet. The radii of curvatures of these surfaces is preferably about 0.010 to 0.025 inch.

The container wall of this invention has a removable sector to which a tab element has been secured by means of a staked integrally formed rivet. The tab element has an upper surface and a lower surface with a rivet receiving opening extending therebetween. The opening is so configurated that it diverges as it extends from the tab upper surface to the tab lower surface. This'divergence is established through the convex curvature of the opening defining wall portion adjacent the lower surface of the tab. The opening defining wall adjacent the upper surface of the pull tab is disposed generally perpendicular to the adjacent top surface of the tab.

It is an object of this invention to provide a method and apparatus for producing a container wall having a removable sector within which an operating tab element is secured by means of an integral rivet with the tab element opening having a generally complementary curved surface in contact with a curved surface of the rivet peripheral wall.

It is another object of this invention to provide such a method and apparatus which will rapidly and economically produce such mating surface to surface con- It is another object of this invention to provide such a method and apparatus which is adapted for use with a wide range of tab materials and tab and rivet configurations.

These and other objects of this invention will be more fully understood and appreciated from the following descriptions of the invention, on reference to the illustrations appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a plan view of one type of tab element employing the concepts of this invention.

FIG. 2 is a sectional view of the tab element illustrated in FIG. 1 taken through line 2-2.

FIG. 3-is a sectional viewof the tab element of FIG. 1 taken through line 3-3.

FIG. 4 is a fragmentary sectional detail of one form of male die element contemplated by this invention.

FIG. 5 is a fragmentary sectional view of one form of female die element contemplated by this invention.

FIG. 6,illustrates a sectional view of a tab being formed between mating male and female dies of this invention.

FIG. 7 is a fragmentary sectional view showing a container wall and tab of this invention during the rivet staking operation.

FIG. 8 illustrates a fragmentary sectional view of a container wall of this invention after rivet staking has been completed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more specifically to the drawings with reference to FIGS. 1 through 3, a metal tab element 2.

of the general type frequently employed in easy open container walls is illustrated. The tab element 2 has a gripping portion 4, which in the form illustrated defines a ring like opening which facilitates manual engagement, and an attaching portion 6 which contains a fastener receiving opening 8 which in the form illustrated is generally circular and is defined by a continuous opening defining wall 10. The tab element has an upper surface 16 and a lower surface 18. The tab is integrally reinforced by hemmed portion 14 to provide: increased strength and rigidity as well as shielding the user from a raw edge. Supplemental integrally formed stiffening ribs 20 are also provided. i

As is shown in FIGS. 2 and 3 the opening defining wall diverges as it extends downwardly from upper tab surface 16 to lower tab surface 18. The upper section 30 of opening defining wall 10 is disposed substantially perpendicular to upper tab surface 16. The lower section 32 of opening defining wall 10 has a convex curvature of radius R This radius of curvature, which is preferably about 0.010 to 0.025 inch, corresponds generally with the radius of curvature of the peripheral rivet wall portion which opening defining wall 10 will contact when the tab is joined to a container wall by staking the integral rivet.

Referring now to FIGS. 4 through 6, the die configurations employed to establish the tab opening configuration of this invention will be described. The male die 40 shown in FIG. 4 has an upwardly directed boss 42 and a surrounding annular tab supporting surface 44. Tab supporting surface 44 is adapted to engage lower tab surface 18. The curved transitional surface between boss 42 and annular tab supporting surface 44 is outwardly concave and has a radius R This radius R preferably approximates that of the rivet peripheral wall portion to which the tab will be secured. The boss 42 has a generally cylindrical lower portion 46 and a convexly curved outer portion 48. The curved outer portion 48 serves as a pilot surface which helps guide the boss 42 of male die 40 into recess 54 of female die 50 during relative closing movement of the male and female dies 40, 50.

The female die 50 shown in FIG. 6 has a recess defining wall 52 surrounding recess 54 and an outwardly disposed annular tab engaging surface 56. Tab engaging surface 56 is adapted to engage upper tab surface 16. The diameter of male die boss 42 is slightly smaller than the diameter of recess 54 of female die 50 in order that the former may enter the latter during fabrication of the tab, but not so much smaller as to permit undesired metal flow therebetween.

FIG. 6 shows male and female dies 40, 50, which are mounted for relative movement, in closed position at the completion of the forming stage. Male die boss 42 has entered recess 54 of female die 50. Annular tab supporting surface 44 of male die 40 and annular tab engaging surface 56 of female die 50 compressively engage tab element 58 adjacent to the opening therein in order to establish radially outwardly directed metal flow..This restraint, coupled with the relatively slight differences between the diameter of male die boss 42 and the diameter of recess 54 of female die 50, serves to positively restrain the upper and lower tab surfaces gainst tab bending or substantial alteration of the size of the fastener receiving opening during the compressive reforming stage. It is seen that the lower portion of opening defining wall 10 has been compressively reformed in order to conform to radius R which is preferably of about 0.010 to 0.025 inch, of male die 40. Supplemental support for the radially outer portions of tab element 58 is provided by collar 60.

Upon completion of the compressive reforming, the

male and female dies 40, 50 are subjected to relative separating movement and the reformed tab element 58 withdrawn.

FIG. 7 shows an unstaked integrally formed rivet 64 and a tab 66 so positioned that the rivet extends through tab opening 68. The sheet element out of which the container wall is formed will generally be metal and preferably is aluminum in a thickness of about 0.008'to 0.015 inch. Integral rivet 64 has transverse end wall 64a and peripheral wall 64b. The lower portion of peripheral wall 64b has a concave curved transition portion 67. The container wall 70 is supported upon staking anvil 72 which has an anvil boss 74 extending into the hollow of integral rivet 64. Adjacent panel supporting surface 76 is in contact with the undersurface of container wall 70. In effecting heading of the rivet, overlying annular pressure pad 80 moves downwardly so as to cooperate with supporting surface 76 of staking anvil 72 in clamping tab 66 and container wall 70. After this has been accomplished, staking punch 82 moves downwardly to contact and axially compress integral rivet 64 to provide a head of enlarged diameter with respect to tab opening 68.

FIG. 8 illustrates in fragmentary section the container end wall 70 having the tab 66 firmly secured thereto by means of headed rivet 64. The complementary curved portions of tab opening defining wall 10 and rivet transitional wall 67' are in intimate curved surface to surface contact which is preferably substantially continuous around the periphery of transitional wall 67. The tab 66 is, therefore, firmly and securely anchored to the container wall 70 and adapted for highly efficient unitary operation during opening of the container by means of the tab element.

It will be appreciated that this invention provides method and apparatus for economically and effectively establishing uniform surface to surface contact between a tab opening defining wall and the adjacent peripheral wall of an integral rivet. This permits effective circumferential engagement between the tab and rivet in regions having curved transitional side walls to provide improved strength and reduce the risk of rivet failure during operation of the opening device. All of this is accomplished without the need for major investment in additional equipment, without the need for major changes in existing tab or rivet fabricating systems and without the need for material redesign of such easy opening devices.

While for purposes of simplicity of illustration the tab element opening has been shown as being generally circular in plan, it will be appreciated that the opening may be provided with an oval configuration or other suitable functional shapes which continuously or partially conform to the rivet wall configuration.

Whereas particular embodiments of the invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details may be made without departing from the invention as defined in the appended claims.

We claim:

1. Apparatus for fabricating a tab element having an opening for joinder to a removable sector of a container wall, including a female die having an elongated recess and an outwardly disposed annular tab engaging surface,

a male die having an upwardly directed boss and a surrounding annular tab supporting surface,

said male die boss having a generally cylindrical lower portion and a convexly curved upper portron,

said male die boss having a diameter less than said tab opening,

said female die annular tab engaging surface being oriented substantially parallel to said male die annular tab supporting surface to compressively engage said tab adjacent said tab opening and reform the tab opening defining wall when said dies are moved to relative closed position,

said annular tab supporting surface of said male die being oriented generally perpendicular to said lower cylindrical portion of said boss, and

a concave male die transition wall connecting said cylindrical portion and said surrounding annular tab supporting surface, whereby positioning said tab element with said opening aligned with said dies and establishing relative closing movement between said dies produces compressive reforming of the opening defining portion of said tab element without substantial tab bending to establish an opening defining wall having a convexly curved portion corresponding in curvature to said concave transition wall.

2. The apparatus of claim 1, including said male die boss having a diameter closely approximating but less than the diameter of said female die elongated recess, with said difference in diameters being such as to permit free entry of said male die boss into said female die recess but preclude substantial metal flow therebetween, and

said concave transition surface of said male die having a radius of curvature of about 0.010 to 0.025 inch.

3. A method of manufacturing a tab element for joinder to a container wall, including providing a tab element having an upper surface and a lower surface with a fastener receiving opening defined by a continuous wall extending from said upper surface to said lower surface,

compressively reforming said tab element adjacent said fastener receiving opening to provide a continuous wall which diverges from said upper tab surface to said lower tab surface, and

simultaneously restraining said upper and lower tab surfaces against substantial tab bending and against substantial enlargement of the size of said fastener receiving opening.

4. The method of claim 3, including forming said opening in said compressively reformed tab element substantially symmetrical about an axis generally perpendicular to said pull tab, and

establishing said diverging continuous wall through generally radially outwardly directed metal flow with respect to said continuous wall to provide a convex curve in said continuous wall adjacent said lower surface of said tab element.

5. The method of claim 4, including establishing said convexly curved continuous wall with a radius of about 0.010 to 0.025 inch. 

1. Apparatus for fabricating a tab element having an opening for joinder to a removable sector of a container wall, including a female die having an elongated recess and an outwardly disposed annular tab engaging surface, a male die having an upwardly directed boss and a surrounding annular tab supporting surface, said male die boss having a generally cylindrical lower portion and a convexly curved upper portion, said male die boss having a diameter less than said tab opening, said female die annular tab engaging surface being oriented substantially parallel to said male die annular tab supporting surface to compressively engage said tab adjacent said tab opening and reform the tab opening defining wall when said dies are moved to relative closed position, said annular tab supporting surface of said male die being oriented generally perpendicular to said lower cylindrical portion of said boss, and a concave male die transition wall connecting said cylindrical portion and said surrounding annular tab supporting surface, whereby positioning said tab element with said opening aligned with said dies and establishing relative closing movement between said dies produces compressive reforming of the opening defining portion of said tab element without substantial tab bending to establish an opening defining wall having a convexly curved portion corresponding in curvature to said concave transition wall.
 2. The apparatus of claim 1, including said male die boss having a diameter closely approximating but less than the diameter of said female die elongated recess, with said difference in diameters being such as to permit free entry of said male die boss into said female die recess but preclude substantial metal flow therebetween, and said concave transition surface of said male die having a radius of curvature of about 0.010 to 0.025 inch.
 3. A method of manufacturing a tab element for joinder to a container wall, including providing a tab element having an upper surface and a lower surface with a fastener receiving opening defined by a continuous wall extending from said upper surface to said lower surface, compressively reforming said tab element adjacent said fastener receiving opening to provide a continuous wall which diverges from said upper tab surface to said lower tab surface, and simultaneously restraining said upper and lower tab surfaces against substantial tab bending and against substantial enlargement of the size of said fastener receiving opening.
 4. The method of claim 3, including forming said opening in said compressively reformed tab element substantially symmetrical about aN axis generally perpendicular to said pull tab, and establishing said diverging continuous wall through generally radially outwardly directed metal flow with respect to said continuous wall to provide a convex curve in said continuous wall adjacent said lower surface of said tab element.
 5. The method of claim 4, including establishing said convexly curved continuous wall with a radius of about 0.010 to 0.025 inch. 